In 1982, as a high school student at Mt. Lebanon High School, Skrenta wrote the Elk Cloner virus that infected Apple II machines. It is widely believed to be one of the first large-scale self-spreading personal computer viruses ever created.[2]

He was involved in the development of VMS Monster an old MUD for VMS. VMS Monster was part of the inspiration for TinyMUD. He is also known for his role in developing TASS, an ancestor of tin,[7] the popular threaded Usenet newsreader for Unix systems. In 1989 he started working on a multiplayer simulation game. In 1994 it was launched under the name Olympia as a pay-for-play PBEM game by Shadow Island Games.[8]